Dr. Angela Peck is a 3rd year fellow in Pediatric Infectious Diseases at the University of Washington. Her long-term goal is an academic career, with a clinical research program that uses novel laboratory assaysto study the epidemiology and pathogenesis of respiratory virus infections among healthy and immuno- compromised patients. She has long-standing interests and research experience in the field of respiratory viruses, and her proposed career development plan incorporates an intense, closely mentored patient- oriented training environment with a plan for a comprehensive didactic curriculum. Dr. Peck will investigate parainfluenza virus (PIV) infections after hematopoietic cell transplant (HCT). PIV infections are not only common, but often severe and fatal in HCT recipients, and frequently cause pulmonary sequelae among long-term survivors. Even upper respiratory infection with PIV is associated with increased mortality after HCT. Preliminary data suggest that PIV infection occurs frequently in the absence of symptomsamong HCT recipients. The overall hypothesis of this proposal is that asymptomatic, or subclinical, PIV shedding in HCT recipients is common, related to host immunologic factors, and may increase PIV transmission to others. For Aims 1 and 2, a cohort of 500 HCT recipients will be followed with nasal wash sampling and serum collection for 1 year after HCT. By testing the respiratory samples for PIV using RT-PCR, these studies will define frequency and duration of PIV shedding, risk factors for symptomatic progression, and correlation of PIV virus quantitation and disease severity. Serum samples from patients in this cohort will be tested for PIV-specific neutralizing antibody, and a nested case-control analysiswill be performed to determine whether humoral immunity is protective against acquisition and progression of PIV infection in HCT recipients. Aim 3 is to develop and validate a new self-collection method of nasal secretions for detection of respiratory viruses by RT-PCR. This method will be compared to nasal washes, the current standard of care. By characterizing PIV infections that occur without symptoms after HCT, and studying factors which affect whether patients acquire PIV and progress to serious disease, these studies may ultimately provide targets for PIV prevention and therapy. Development of a self-collection method will allow for frequent sampling in outpatients, and provide a foundation for future studies of PIV pathogenesis and transmission.